Embodiments of the present invention relate to an array substrate and a method for manufacturing the same, and an OLED display device.
Among various display devices available now, an OLED (Organic Light-Emitting Diode) display has a lighter and thinner profile design, a wider visible angle, a faster response speed, a lower power consumption and other features as compared to a CRT (Cathode Ray Tube) display or a TFT-LCD (Thin Film Transistor-Liquid Crystal Display), and so the OLED display has gotten people's attention as the next generation of display devices gradually.
The OLED display device is a self-luminous device, which usually includes a pixel electrode, a counter electrode disposed in opposition to the pixel electrode and an organic light emitting layer disposed between the pixel electrode and the counter electrode. In the OLED display device, by means of applying a voltage to the pixel electrode and the counter electrode, an electric field is formed across the organic light emitting layer disposed between the pixel electrode and the counter electrode, so that electrons and holes can recombine with each other in the organic light emitting layer to give off light. The voltage applied to the pixel electrode can be controlled by an array substrate with circuit units, so as to control the display effect of the OLED display device.
In the related art, in order to control the display effect of the OLED display device better, the circuit units of the array substrate generally adopt a structure of two TFTs (Thin Film Transistors), in which, a first TFT is a switch transistor, and a second TFT is a drive transistor. The partial structure of pixel units is illustrated in FIG. 1, and FIG. 2 is a cross-sectional view in the direction of A-A of FIG. 1. In FIG. 1, a gate line 13 is connected to a gate electrode (i.e. a first gate electrode 111) of a TFT 11, a data line 14 is connected to a source electrode (i.e. a first source electrode 112) of the TFT 11, and a first drain electrode 113 of the TFT 11 is connected to a gate electrode (i.e. a second gate electrode 121) of a TFT 12 through a via hole a. A Vdd line 15 parallel to the data line 14 is connected to a source electrode (i.e. a second source electrode 122) of the TFT 12, a second drain electrode 123 of the TFT 12 is connected to a pixel electrode 16. As can be seen from the sectional drawing FIG. 2, two TFTs are formed on a substrate 10, and each adopt a bottom-gate structure, and a gate insulating layer 101, an active layer 102 formed of an oxide and an etching blocking layer 103 are further formed on the first gate electrode 111 and the second gate electrode 121 in sequence. The first drain electrode 113 is connected to a connecting electrode 17 through the via hole a, and the second gate electrode 121 is connected to the connecting electrode 17 through a via hole b, so the first drain electrode 113 and the second gate electrode 121 can be connected by the connecting electrode 17 in the same layer as the pixel electrode 16. To avoid short circuit between the connecting electrode 17 and other electrode, the coverage zone of the pixel electrode 16 should keep away from the region where the connecting electrode 17 is located. As shown in FIG. 1, an organic light emitting layer 18 disposed on a corresponding pixel electrode 16 should also keep away from the region where the connecting electrode 17 is located, which needs to be covered by a light shielding material 19, and a counter electrode 110 is provided on surfaces of the organic light emitting layer 18 and the light shielding material 19, so as to constitute an OLED display device.
Due to existence of the connecting electrode 17, the region where the connecting electrode 17 is located needs to be covered by a black matrix, so that the area of an effective emitting zone of the OLED display device is decreased, and the display brightness is reduced. On the other hand, the array substrate of the OLED display device with such a structure needs to experience seven mask procedures from provision of a gate electrode to provision of a pixel electrode, so as to form a gate layer, a gate insulating layer, an active layer, an etching blocking layer, a source and drain electrode layer, a resin layer and a pixel electrode and a connecting electrode. Also, to connect the first drain electrode 113 and the second gate electrode 121, it is necessary that a plurality of via holes be provided on the substrate, which will cause the fabrication process of the OLED display device to be more complex. Thus, the production difficulty and the production cost of products are largely raised.